1. Field of the Invention
The present invention relates generally to support systems for clothing and body worn equipment, and more particularly, to active support systems for clothing, equipment and/or other body worn items including jackets, backpacks, football helmets/pads, and other military and non-military clothing and gear. The invention actively off-loads bodyworn item loads to reduce back fatigue, and also during a seated shock event for enhanced protection of the wearer.
2. Description of Prior Art
Occupant survivability is a top priority for the design of military ground vehicles as more than 4,400 casualties in recent conflicts, or over 60% of the total casualties, have been the result of the effects of Improvised Explosive Devices (IEDs) on ground vehicles. Operational demand for ground vehicles in areas with high potential for IEDs has increased, and this accentuates the need for enhanced war-fighter protection to vehicular underbody blast events. In addition to the extreme forces resulting from explosive devices, it has been shown that shock and vibration resulting from normal vehicular operations leads to fatigue, back pain, and long-term chronic injuries which result in premature departure of highly trained individuals. Energy absorbing (EA) systems are used within the seat mountings of vehicles to attenuate the loads transmitted to the occupants. These offer protection to soldiers in case of extreme IED events. One such system is an adaptive seating suspension utilizing an actively controlled magnetorheological (MR) fluid based dampener to provide optimized occupant protection to extreme shock events and also to provide vibration control during normal vehicle operation. As described more fully in U.S. Pat. No. 7,822,522 which is incorporated herein by reference, these systems automatically adapt to occupant weight and environmental conditions (e.g. blast severity and vibration profiles) and have been proven to provide optimized protection while minimizing required seat stroke.
The amount of equipment that soldiers and aviators are required to bear upon their upper torso contributes to the problem. The average weight of such equipment has increased from 5-6 lbs in the 1970s-1980s to upwards of 80-100 lbs today. This can more than double the total mass supported by an individual's spine, which significantly increases the chances of acute injuries (during extreme events) as well as long-term chronic injuries from normal operations. For example, 80 lbs of additional lumbar-supported equipment weight for a soldier experiencing a 20 G pelvic acceleration increases the lumbar compression load by 1600 lbs which roughly doubles the expected lumbar load as compared to the same event without the additional equipment. Such a load is above the allowable tolerance for spinal injury under some metrics. One widely utilized performance metric for blast survivability is the Dynamic Response Index (DRI) which was developed in the late 1960's and 1970's for ejection seats and which utilizes a second order differential equation with assumed biodynamic properties (mass, stiffness, damping) to estimate the likelihood of spinal damage. However, this metric utilizes only a pelvis or seat pan acceleration profile for input and assumes a 50th percentile aviator with minimal lumbar-supported equipment. As a result, an acceleration profile which passes DRI may be entirely insufficient to protect a modern, gear laden vehicle occupant. The same is true for other acceleration-based injury metrics (7 millisecond clip, Eiband, etc.) because the tolerable levels were identified with much lower lumbar-supported mass levels.
Studies are underway to update and develop new injury tolerance metrics based either on spinal (lumbar) load or, if acceleration based, will at least take into account the additional equipment masses that the modern warfighter is expected to wear. These new/updated metrics will have an alarming effect on the perceived performance of currently fielded seating solutions because they will show that many such systems provide inadequate protection.
More recent studies by experts in vehicular occupant safety have shown that seat based attenuation systems would require an increased seat stroke of 60-80% to maintain lumbar loads within current tolerance levels with a mass of lumbar-supported equipment of about 45 lbs. This is difficult if not impossible since seat stroking distance is already limited and overmatched by blast forces.
One solution to the problem of increased lumbar-supported weight is simply to off-load the spine but this is not practical from an operation perspective because much of this equipment is mission and/or safety critical. Methods of alternatively supporting the additional equipment/mass by other structure such as the vehicular seat are possible but suffer from concerns of limited mobility and hindered vehicular egress. What is needed is an independent or integrated lumbar support system able to supplement the human body's ability to support weight on the upper torso. Such a system would need to be lightweight, unobtrusive so as not to hinder movement, independently powered (or passive, i.e., unpowered), and capable of quickly adapting to a variety of environmental variables to protect the spine of the wearer in a range of high shock or repetitive shock events.